This invention relates generally to an electrophotographic printing machine, and more particularly concerns an improved paddle wheel substrate feeding system for feeding substrates, which term is used herein to include sheets of any type, from a stack along a predetermined path.
Feeding sheets from a stack may be viewed as involving three separate problems. The first is separating a sheet or sheets from a stack. The second is queuing the separated sheets into an order such as that corresponding to their order in the stack, e.g. outermost sheets followed by the adjacent intermost sheets. The third problem is advancing the queued sheets into the sheet processing system being served by the feeding mechanism.
Sheet separation with a belt and retard roller appear in the sheet handling art at least as early as 1916 in U.S. Pat. No. 1,167,367 to P. L. Wells and as recently as 1969 in U.S. Pat. No. 3,469,834 to Stange et al. The separation belt and retard roller are employed in these patents for queuing and advancing the sheets but not for separating them from the stack. In the patents, the region of contact between the roller and belt form a sheet queuing throat which is able to "fan out" or queue sheets passed through it. The sheets are separated from a stack and fed to the throat by a presser foot in the Wells, U.S. Pat. No. 1,167,367 and by a nudger or feed wheel in the Stange et al, U.S. Pat. No. 3,469,834.
In addition, numerous devices such as impact/paddle feeders of the type disclosed in U.S. Pat. No. 3,630,516 have been employed to minimize the possibility of mis-feeds or multi-feeds. The continued search for feeders that minimize mis-feeds and multi-feeds and can handle wider ranges of copy paper or documents have been necessitated by the complexity of modern sheet processing machines, such as, printers, sorters, collators, reproduction machines, etc., since a mis-feed or multi-feed causes machine shut downs. As an improvement, the present top feeder combines friction retarding and paddle wheel feeding to provide for low cost but reliable single sheet separation and feeding from a stack.